A long-term study of a snake community in north-western Tuscany (central Italy): population structure and density patterns

Federico Storniolo,Sacha Menichelli,Marco A.L Zuffi

doi:10.3897/herpetozoa.32.e35574

Abstract

We analysed a snake species community of a Mediterranean 0.2 ha ecotonal area during a 21 year time span, monitoring two colubrid and one viperid snake species. We carried out analyses in seven years (1997, 1999, 2002, 2004–2005, 2016–2017) that had similar sampling efforts and, in the last two years of short-term monitoring, we applied a recently proposed monitoring protocol of the Italian Environment Ministry. In total, we captured 172 distinct individuals, 61 whip snakes (Hierophisviridiflavus), 26 barred grass snakes (Natrixhelvetica) and 85 asp vipers (Viperaaspis). Regarding the long-term monitoring period, whip snakes were captured on average about nine times per year, grass snakes were captured four times per year and asp vipers were found 12 times per year. Captures decreased in whip snakes, while increased in grass snakes and remained constant in asp vipers. In 2016 and 2017, we captured 10 whip snakes, 19 grass snakes and 31 asp vipers. Density estimates of snake species (0.5 H.viridiflavus/ha, 0.3 N.helvetica/ha and 0.7 V.aspis/ha) differ, to a certain extent, from published results for some other areas of central, northern and western Europe, perhaps depending on the approach applied for habitat suitability estimation. The average body size between two years differed neither for whip snakes nor for grass snakes, but it decreased significantly in asp vipers.

Highlights

Modern biological and zoological research have shown the importance of snakes in environmental studies as indicator species (Landres et al 1988) in terms of habitat use, activity patterns, reproduction and diet (Scali and Montonati 2000; Rugiero et al 2002; Filippi et al 2005; Capula et al 2006; Row and Blouin-Demers 2006), relatively few studies have been performed for long-term analyses
Density estimates of snake species (0.5 H. viridiflavus/ha, 0.3 N. helvetica/ha and 0.7 V. aspis/ha) differ, to a certain extent, from published results for some other areas of central, northern and western Europe, perhaps depending on the approach applied for habitat suitability estimation
Over a much longer period, population decline has been assessed in Drymarchon couperi (Godley and Moler 2013) and long term snake community dynamics have been analysed by Fitch (1999) in North America, during a 50 year period

Summary

Introduction

Modern biological and zoological research have shown the importance of snakes in environmental studies as indicator species (Landres et al 1988) in terms of habitat use, activity patterns, reproduction and diet (Scali and Montonati 2000; Rugiero et al 2002; Filippi et al 2005; Capula et al 2006; Row and Blouin-Demers 2006), relatively few studies have been performed for long-term analyses (see Reading et al 2010 for comprehensive review and discussion). Population average body size varied significantly amongst years for each species (H. viridiflavus: F=2.244, df=6, P=0.037; N. helvetica: F=5.892, df=4, P=0.003; V. aspis: F=7.299, df=6, P < 0.0001) (Table 3).

Results

Conclusion